Electrosurgery is now a widely used surgical method for treating tissue abnormalities. One class of electrosurgical abalation devices are so-called monopolar electrosurgical devices. Typically such ablation devices include an electrosurgical probe having a first or “active” electrode extending from one end. The electrosurgical probe is electrically coupled to an electrosurgical generator, which provides a high frequency electric current. A remote control or hand-activated switch is attached to the generator and commonly extends to a foot switch located in proximity to the operating theater. During an operation, a second or “return” electrode, having a much larger surface area than the active electrode, is positioned in contact with the skin of the patient (e.g., a patch). The surgeon may then bring the active electrode in close proximity to the tissue and activate the foot control switch, which causes electrical current to arc from the distal portion of the active electrode and flow through tissue to the larger return electrode.
Still other electrosurgical abalation devices are classified as bipolar-based. In these devices no return electrode is used. Instead, a second electrode is closely positioned adjacent to the first electrode, with both electrodes being attached to an electrosurgical probe. As with the monopolar-based devices, the electrosurgical probe is electrically coupled to an electrosurgical generator. When this generator is activated, electrical current arcs from the end of the first electrode to the end of the second electrode, flowing through the intervening tissue. In practice, several electrodes may be employed, and depending on the relative size or locality of the electrodes, one or more electrodes may be active.
Whether arranged in a monopolar or bipolar fashion, the active electrode may be operated to either cut tissue or coagulate tissue. When used to cut tissue, the electrical arcing and corresponding current flow results in a highly intense, but localized heating, sufficient enough to break intercellular bonds, cellular membranes, and cellular contents, resulting in tissue severance. When used to coagulate tissue, the electrical arcing results in a low level current that denatures cells to a sufficient depth without significant breakage of intercellular bonds, i.e., without cutting the tissue.
There are many medical procedures in which tissue is cut or carved away for diagnostic or therapeutic reasons. For example, during hepatic transection, one or more lobes of a liver containing abnormal tissue, such as malignant tissue or fibrous tissue caused by cirrhosis, are cut away. There exists various modalities, including mechanical, ultrasonic, and electrical (which includes RF energy), that can be used to effect the resection of abnormal tissue. Regardless of which modality is used, however, extensive bleeding can occur, which can obstruct the surgeon's view and lead to dangerous blood loss levels, requiring transfusion of blood, which increases the complexity, time, and expense of the resection procedure. To prevent extensive bleeding, hemostatic mechanisms, such as blood inflow occlusion, coagulants (e.g., Surgicel™ or Tisseel™), and energy coagulation (e.g., electrosurgical coagulation or argon-beam coagulation), can be used.
In the case where an electrosurgical coagulation means is used, the bleeding can be treated or avoided by coagulating the tissue in the treatment areas with an electro-coagulator that applies a low level current to denature cells to a sufficient depth without breaking intercellular bonds, i.e., without cutting the tissue. Because of their natural coagulation capability, ease of use, and ubiquity, electrosurgical modalities are often used to resect tissue.
During a typical electrosurgical resection procedure, electrical energy can be conveyed from an electrode along a resection line in the tissue. The electrode may be operated in a manner that incises the tissue along the resection line, or coagulates the tissue along the resection line, which can then be subsequently dissected using the same coagulation electrode or a separate tissue dissector to gradually separate the tissue. In the case where an organ is resected, application of RF energy divides the parenchyma, thereby skeletonizing the organ, i.e., leaving vascular tissue that is typically more difficult to cut or dissect relative to the parenchyma.
When a blood vessel is encountered, RF energy can be applied to shrink the collagen contained in the blood vessel walls, thereby closing the blood lumen and achieving hemostasis. The blood vessel can then be mechanically transected using a scalpel or scissors without fear of blood loss. In general, for smaller blood vessels less than 3 mm in diameter, hemostasis may be achieved within 10 seconds, whereas for larger blood vessels up to 5 mm in diameter, the time required for hemostasis may increase to 15-20 seconds. During or after resection of the tissue, RF energy can be applied to any “bleeders” (i.e., vessels from which blood flows or oozes) to provide complete hemostasis for the resected organ. This may be accomplished by employing the same device used for cutting.
When electrosurgically resecting tissue, care must be taken to prevent the heat generated by the electrode from charring the tissue, which generates an undesirable odor, results in tissue becoming stuck on the electrosurgical probe, and most importantly, increases tissue resistance, thereby reducing the efficiency of the procedure. Adding an electrically conductive fluid, such as saline, to the electrosurgery site reduces the temperature of the electrode and keeps the tissue temperature below the water boiling point (100° C.), thereby avoiding smoke and reducing the amount of charring. The electrically conductive fluid can be provided through the probe that carries the active electrode or by another separate device.
Although the application of electrically conductive fluid to the electrosurgery site generally increases the efficiency of the RF energy application, energy applied to an electrode may rapidly diffuse into fluid that has accumulated and into tissue that has already been removed. As a result, if the fluid and removed tissue is not effectively aspirated from the tissue site, the electrosurgery may either be inadequately carried out, or a greater than necessary amount of energy must be applied to the electrode to perform the surgery. Increasing the energy used during electrosurgery increases the chance that adjacent healthy tissues may be damaged. At the same time that fluid accumulation is avoided, care must be taken to ensure that fluid is continuously flowed to the tissue site to ensure that tissue charring does not take place. For example, if flow of the fluid is momentarily stopped, e.g., if the tube supplying the fluid is kinked or stepped on, or the port on the fluid delivery device becomes clogged or otherwise occluded, RF energy may continue to be conveyed from the electrode, thereby resulting in a condition where tissue charring may occur.
A related concern with existing electrosurgical ablation devices is that heat generated at the application site rapidly dissipates away from the treated area of interest. It is preferable, however to localize the elevated temperatures (and coagulation effect) to the application site. Heat energy that is dissipated away from the application site has the potential to damage or destroy healthy tissue. In addition, heat dissipation requires that additional energy be applied to the electrode which, as stated above, increases the probability that adjacent healthy tissues may be damaged or destroyed.
While electrosurgical resection of tissue reduces the amount of blood loss, as compared to other tissue resection modalities, it still involves a tedious process that includes painstakingly cutting/dissecting through the parenchyma and ligating and cutting through blood vessels. Moreover, because time is of the essence in such procedures there is a need to reduce the amount of time wasted in manipulating and switching between multiple instruments. It is generally desirable to provide as much functionality in a single device to avoid the use of multiple devices having separate functions. Similarly, the use of multiple devices often requires one or more surgeons or other trained personnel to assist.
There remains a need for resection devices and methods that can be used to efficiently resect vascularized tissue. Similarly, there is a need for such devices and methods to effectuate and maintain hemostasis at the treatment site. There is also a need for resection methods and devices that reduce or eliminate the need for a physician to switch between different surgical instruments.